Need help improving my post processing

[MylesGibson]

So I have only been imaging for about a year, and I think my processing has come on a bit since I started, but I am still struggling to get truly pleasing results. Maybe there is something wrong with my data, or maybe my post processing skills are poor, or perhaps I'm just doing something wrong. I am hoping someone can assist in finding out which is the issue so I can work on it!

My current imaging equipment is with a Canon 1000D, through an Altair Starwave 102ED-R. I don't have any filters and the camera is unmodified. 

The other night, I took 62 images at 300s of M33. This gives me just over 5 hours total which I thought would be more than enough for a pleasing image. I have 50x bias frames I took about a month ago, 20x dark frames from a few nights previously, and 40 flat frames I took after the imaging session.

I use DeepSkyStacker to stack the images, and Photoshop CS3 to do the post processing. 

I saw a tutorial on processing images about a year back and since then, I just seem to stick with the same steps repeatedly without really knowing what it's doing, so I haven't been able to improve as much as I wanted to. I'll go through my steps, then attach the stacked TIFF file in case anyone wants to have a go and show me what could be done with good skills! And also, I welcome people to tell me what I can do to improve, what I am doing wrong etc.

These are the settings I use in DSS, which I had set up ages ago from a tutorial and have never changed:

This is the first bit that concerns me. I counted all of my flat and dark frames, but DSS is telling me there are only 10 darks and 29 flats? Could this be because they have been used previously or something? Also, I don't really know what the Kappa-Sigma stuff does, it was just recommended so I use that.

Now to the actual processing part....

First thing I do is go to Image --> Mode --> 16 bit so I can actually do something with the image, then as it is a bit off center, I'll crop it to get it central in the frame.

I then "stretch" the image. This method is again from the old tutorial and it's just something I have always done without thinking or questioning. I go into Curves, then stick a point anywhere. I then change the Input to 11, and Output to 4:

For all I know, this is a poor method of stretching, btu it's what I have known and continue to do.

Next, I go to Levels. Here, I individually select the Red, Green and Blue parts from the drop-down and move the black point over to the right, until it is a little bit before the peak:

I repeat that for each channel. I then repeat this step as I get a bit more control, and this time, bring the grey over to the left, until its just in front of the start of the peak, as well as bringing the black in to the beginning of the peak, making sure not to clip it.

Once again, I repeat this for each channel.

Sometimes, this makes the image really noisy. If it does, I just delete that step. I then flatten the image.

Next, back into curves. I set an "anchor" for the background then move the curve around a bit till it kind of looks ok to me.

I then go back into levels and repeat the stage from earlier. The image in once again flattened. 

Even with flats, at this point I always have a colour gradient, and the background sky colour doesn't look right. I bought something called Astronomy Tools for photoshop, so I tend to just play around with those after this bit, usually doing the colour gradient removal, light pollution removal enhanced flatten and then reduce star halos. 

So I don't really do anything fancy, as I don't really know my way around photoshop too well. 

Anyway, here's the result:

I seem to have barely any colour, apart from some blue CA on the stars. I have used this method with other galaxies and nebulae etc and picked up nice colours, so not sure what happened here. I have seen people bring out more detail with far less data using less exposure time.

I have attached my stacked TIFF file if people want to have a go themselves, and you can let me know if I just have poor data. But if the data is good, I would really appreciate any help with post processing techniques, even if it's to tell me that what I do is completely wrong and horrible and to rethink the whole thing. I'd love to learn some new techniques and not only that, know why I am using them

 

 

Please help!

 

M33 Stacked.tif

[MarkAR]

I would look at Gimp for processing as a starter. Very similar to Photoshop but free.

[MylesGibson]

3 minutes ago, MarkAR said:

I would look at Gimp for processing as a starter. Very similar to Photoshop but free.

I have used it before, but didn't really get on with it. I don't think that's really the problem here though.

[gilesco]

I'm no expert, but for your brightness curves - you probably want to increase the y axis gradient for where you have data, then perhaps stretch afterwards.

[MarkAR]

Just had a quick play using Mac Photos' editing and there is some colour there.

[MarkAR]

Maybe have a look at Pixinsight.

[steppenwolf]

There is some colour in there but my very quick process is still a little too magenta for my liking but it is an indication of what is there. In fairness, M33 is a rather tricky object to tackle!

Your workflow is very different from mine but that doesn't mean that it is wrong!! However, starting with your 32 bit TIF, I processed the data in PhotoShop starting with Levels first on the whole RGB image and making numerous iterative changes to both the black and white points until I had enough to balance the colours so that their intensities were similar - again I used levels for this, adjusting the red, green and blue channels separately. This latter process got rid of much of the light pollution in the image.

I then continued with Levels adjustment until I had a reasonably attractive image with a background level of between 22 and 24 in the Histogram display for each colour. Once I had achieved the background level I wanted, I pinned the 'black' level at 23 and raised the rest of the histogram in Curves. This resulted in over-bright stars so I reduced them using the 'halo removal' tool in Noel Carboni's Actions followed by a further pinned Curves boost and a final tweak with Hue and Saturation.

[MylesGibson]

50 minutes ago, MarkAR said:

Just had a quick play using Mac Photos' editing and there is some colour there.

 

Glad that there is some colour! Just need to bring it out!

59 minutes ago, gilesco said:

I'm no expert, but for your brightness curves - you probably want to increase the y axis gradient for where you have data, then perhaps stretch afterwards.

How do you mean increase the Y axis gradient? 

 

50 minutes ago, MarkAR said:

Maybe have a look at Pixinsight.

I am not meaning to sound rude, but I don't think suggesting different software programs is going to help.

41 minutes ago, steppenwolf said:

There is some colour in there but my very quick process is still a little too magenta for my liking but it is an indication of what is there. In fairness, M33 is a rather tricky object to tackle!

Your workflow is very different from mine but that doesn't mean that it is wrong!! However, starting with your 32 bit TIF, I processed the data in PhotoShop starting with Levels first on the whole RGB image and making numerous iterative changes to both the black and white points until I had enough to balance the colours so that their intensities were similar - again I used levels for this, adjusting the red, green and blue channels separately. This latter process got rid of much of the light pollution in the image.

I then continued with Levels adjustment until I had a reasonably attractive image with a background level of between 22 and 24 in the Histogram display for each colour. Once I had achieved the background level I wanted, I pinned the 'black' level at 23 and raised the rest of the histogram in Curves. This resulted in over-bright stars so I reduced them using the 'halo removal' tool in Noel Carboni's Actions followed by a further pinned Curves boost and a final tweak with Hue and Saturation.

 

Wow, you have managed to get a far, far superior end result than I did! And for a very quick process, you've done better than I did in about 45 minutes worth of meddling! I always assumed M33 is quite easy, I didn't realise it's a tricky object? You say your workflow is different from mine, would you mind me asking what it is? Mine was just from an old tutorial I found somewhere and I tend to just stick with it and not stray too far, or doing anything different, or using different tools! So looking at other workflows will help me expand what I do.

Do you not move the grey slider in levels then? Just the black and white? You say you made changes till the colours were balanced and intensities similar, how do you check that?

When you say you continued with the levels adjustments, was this with each channel separately, or as an RGB? And how do you check the background level?

I'll have another little go later following your way and see if it improves things, then maybe work from there! Thank you for this reply. Nice to know I do have some useful data there!

[steppenwolf]

5 minutes ago, MylesGibson said:

Do you not move the grey slider in levels then? Just the black and white? You say you made changes till the colours were balanced and intensities similar, how do you check that?

Ooops, for white replace grey!! I don't use the white slider at all. To 'balance' the colours, I open the Histogram view, and set the RGB display to 'Colors (sic)'. Next I invoke Levels and adjust the Grey level of the two extreme colours (i.e. those that are shown kin the histogram view as being either side of whatever the central colour is) until all three colours overlap.

11 minutes ago, MylesGibson said:

You say your workflow is different from mine, would you mind me asking what it is?

Essentially as discussed in my first post:-

1. use 'Levels' to adjust the RGB levels together to get a brighter image using an iterative process, i.e. moving the grey slider to the left in small increments to brighten the image and the black slider to the right to bring the background brightness back down.

2. balance the colours as already described

3. once the background is right and the image bright but not burnt out, I invoke 'Curves', pin the background at around a figure of 23 by clicking on the background using the Curves selection pipette (with the sample size set to 3 x 3) until I find a suitable location in the dark part of the background with a sample figure of 23. I then press the 'Ctrl' key and click on the same location to 'pin' the bottom of the curve at 23 then increase the rest of the curve to get the brightness that I want

4. work on the stars if they are over-blown (as was the case with your image) - the stars had strong halos after the Curves stretch so I used the Noel Carboni halo removal 'Action' to remove the halos

5. make adjustments using the 'Hue and Saturation' tool to taste

6. make final adjustments using the Curves tool again

27 minutes ago, MylesGibson said:

When you say you continued with the levels adjustments, was this with each channel separately, or as an RGB?

With the full RGB set, all colours together

28 minutes ago, MylesGibson said:

And how do you check the background level?

Set the 'colour picker tool' to a sample size of 3 x 3 then invoke the 'Curves' tool to sample the background and note the level of both input and output then adjust Levels black slider, resample until you get the required level

 

[MylesGibson]

7 minutes ago, steppenwolf said:

Ooops, for white replace grey!! I don't use the white slider at all. To 'balance' the colours, I open the Histogram view, and set the RGB display to 'Colors (sic)'. Next I invoke Levels and adjust the Grey level of the two extreme colours (i.e. those that are shown kin the histogram view as being either side of whatever the central colour is) until all three colours overlap.

Ahh, I had never touched the white before so I was wondering if I had missed a trick there! I didn't know tat you could do that with the histogram view! That is useful to know.

31 minutes ago, steppenwolf said:

3. once the background is right and the image bright but not burnt out, I invoke 'Curves', pin the background at around a figure of 23 by clicking on the background using the Curves selection pipette (with the sample size set to 3 x 3) until I find a suitable location in the dark part of the background with a sample figure of 23. I then press the 'Ctrl' key and click on the same location to 'pin' the bottom of the curve at 23 then increase the rest of the curve to get the brightness that I want

That's something else I wasn't aware of! 

32 minutes ago, steppenwolf said:

4. work on the stars if they are over-blown (as was the case with your image) - the stars had strong halos after the Curves stretch so I used the Noel Carboni halo removal 'Action' to remove the halos

This is the toolset that I have, so this is something I do the same as you!

33 minutes ago, steppenwolf said:

With the full RGB set, all colours together

Set the 'colour picker tool' to a sample size of 3 x 3 then invoke the 'Curves' tool to sample the background and note the level of both input and output then adjust Levels black slider, resample until you get the required level

I get to the colour picker tool by clicking the background colour on the left hand menu. I can't see anything there to set a sample size though?

Thank you very much again for your reply. That was very helpful and has shown me a few more little things I wasn't aware of in Photoshop I can implement. I've now had another go at it, and I am much more pleased than my original effort by combining my original workflow with some of your tips.

Still needs a little bit of work, but much improved I think

[steppenwolf]

1 hour ago, MylesGibson said:

I get to the colour picker tool by clicking the background colour on the left hand menu. I can't see anything there to set a sample size though?

This is the tool I am referring to (sorry was doing all the above from memory).......

[MylesGibson]

22 minutes ago, steppenwolf said:

This is the tool I am referring to (sorry was doing all the above from memory).......

Ahhhh, thanks!

[wimvb]

This is what PixInsight does to your data.

 

There's a magenta/red patch that doesn't look like it should be there, but otherwise there's not much of a problem. But you do have strong blue haloes around your stars that are most likely caused by chromatic aberration.

Edited September 30, 2020 by wimvb

[wimvb]

To bring out the colour, I used arcsinh stretch, which is also available for photoshop. Arcsinh stretch is very good at preserving colour.

I increased saturation in the galaxy. Like you've said already, there are strong blue haloes around the stars. I used a halo mask (Blue channel - Green channel) and then desaturated the blue with PI's colour saturation tool. I would suspect that there is an equivalent tool in PS, where you can change the saturation of only one colour.

Hope this helps

 

Edit:

Btw, how much light pollution do you have? 300 s subs would seem ok, unless you take them at a low ISO setting. If you have light pollution, you need to take more subs to get rid of the noise that comes with LP. More data is always the best noise reduction tool. And the less noise you have, the harder you can push the data.

Edited September 30, 2020 by wimvb

[JamesF]

17 minutes ago, wimvb said:

To bring out the colour, I used arcsinh stretch, which is also available for photoshop

Is this available natively?  I have one that is allegedly a "fair" approximation done as actions, but if it can be done directly please tell me more.

James

[wimvb]

5 hours ago, JamesF said:

Is this available natively?  I have one that is allegedly a "fair" approximation done as actions, but if it can be done directly please tell me more.

James

Arcsinh stretch was developed for Pixinsight and photoshop by SGL member Mark Shelley, @sharkmelley. If you look in his profile for topics he started, you should find more information. Mind you, you will have to look a few years back.

[MylesGibson]

8 hours ago, wimvb said:

To bring out the colour, I used arcsinh stretch, which is also available for photoshop. Arcsinh stretch is very good at preserving colour.

You are the third person I have seen that has mentioned this method. Is this an add-on, or something like that? Or is it a method? Do you know where it may be located in Photoshop?

8 hours ago, wimvb said:

There's a magenta/red patch that doesn't look like it should be there, but otherwise there's not much of a problem. But you do have strong blue haloes around your stars that are most likely caused by chromatic aberration.

Yeah, I did notice that at the top, but I cropped it out when I was done. The blue halos are far reduced from how they used to be with my old scope, although I was hoping they wouldn't be as noticeable with this one. Although I suppose the longer the exposure, the more noticeable it will be due to more light gathered. Am I correct in that way of thinking?

8 hours ago, wimvb said:

Btw, how much light pollution do you have? 300 s subs would seem ok, unless you take them at a low ISO setting. If you have light pollution, you need to take more subs to get rid of the noise that comes with LP. More data is always the best noise reduction tool. And the less noise you have, the harder you can push the data.

I live on the outskirts of a city center, so the LP can be pretty bad. I take my subs at 800 ISO from my garden. I have often thought about adding data from multiple nights, but I don't have a permanent setup, so it gets disassembled and reassembled every time so I would have to take flats each time and I don't know if different flats over different nights would mix very well. 

Thank you very much for the response and some tips about the method though. 

[johneta]

You mention having stuck to the same tutorial and techniques over the first year of processing.
Look around alot more than that. Watch a whole lot more tutorials to inspire you, and I found I just focus on one issue at a time.

Having trouble with colour in image - search that, and solve that issue. Then move on,- best way to use curves. Or getting background colour balanced.
Read widely

Also, I used DSS for ages but was never happy with it. Pixinsight is great but I now use 'Siril' for stacking and initial processing because I'm cheap (its free) and it is very good IMO.

[wornish]

You can get the arcsinh stretch for PS from here.

 

https://www.cloudynights.com/topic/595610-photoshop-color-preserving-arcsinh-stretch/

[MylesGibson]

13 minutes ago, wornish said:

You can get the arcsinh stretch for PS from here.

 

https://www.cloudynights.com/topic/595610-photoshop-color-preserving-arcsinh-stretch/

Thank you for that! I'll have a little play with that tonight